As a standalone class though what we can see is (1) severe lack of damage for the high cast time and CD of skills and (2) lack of real utility in terms of group play.
First point is the most notorious in my pov, for a rank 6 class Rune of Justice and Rune of Destruction do laughable damage given their super high cast time and cooldown, especially when you consider how bad they are to actually hit enough targets to even matter. So basically RoD/RoJ have moderate “Skill Factors/CD” ratios, while having poor AoE potential and even worse aiming potential for Rune of Justice. They both need much much higher skill factors and AoE atk ratios to be even worth mentioning as AoE bursts.
Second one, well let’s start by stating there’s no real reason to waste a buff slot for rune of protection at all in group play, be it pvp or pve. Clerics do it better, period. Hell, even dispellers (or the miko one I can’t remember the name) do it better on average. Now for Rune of Giants, I still can’t see what they intended that skill to be used for. There’s clearly no real point to using it in a general gameplay scenario.
From the whole kit, only rune of ice actually makes sense into wizard build-making. Even with the post-balacing nerf, it’s still great and very useful for cryos and cryo-kinos/elementalists alike. The high cast time though could get soem love and be lowered so it’s easier to set up.
Apart from that, the class severely lacks useful atributtes. Skills themselves are lacking as previously stated, but rune caster as a Hidden class - with a really nice lore behind it btw - has also no atributes to differentiate it from any other generic damage/utility class. The quick cast attribute made little to no sense before, but now that quick cast has much longer upkeep, it’s totally ignorable to say the least.
Still, Rune Caster has my favorite wizard costume lol, so I’m keeping one. I just hope someday i’ll get more use out of it than simply looking good!